I. Field of the Invention
The present invention relates generally to fluid filtering devices and, more particularly, to a fluid filtering device with a filter element bypass means.
II. Description of the Prior Art
There are, of course, a number of previously known fluid filtering devices which are adapted for connection in series with a fluid line in a fluid system. Such a fluid system can, for example, comprise a hydraulic system in which the fluid filtering device is connected to either the suction line from a hydraulic reservoir and to the hydraulic system or the return line from the hydraulic system and to the fluid reservoir. It is necessary to maintain fluid flow in case of suction line filter installations in order to prevent pump cavitation with resultant erosive pump damage as well as power loss and noise. Fluid flow continuity must also be provided for in the case of pressure line and return line filter installations without a clogged filter causing damagingly high pressures.
It is well known in the art of fluid filtering devices that as a filter element becomes increasingly clogged with debris, the pressure drop across the filter element likewise increases and eventually may also diminish the outlet flow from the filter element. As the decrease in fluid flow, or the pressure, or both, become excessive, it can cause one or more of the aforementioned problems.
In order to protect the hydraulic or other fluid system from reduced fluid flow resulting from a clogged filter element, many previously known filtering devices include bypass means for bypassing the fluid flow around the filter element at a predetermined pressure drop across the filter element which is indicative of excess filter clogging. These previously known bypass means, however, are disadvantageous for several different reasons.
One disadvantage of these previously known bypass valves is that such valves are oftentimes complex in construction and are comprised of a multiplicity of separate elements. The complexity of these previously known bypass valves not only increases the initial construction or manufacturing costs of such valves but, in addition, such bypass valves are prone to failure since failure of any one of the numerous bypass valve components can render the valve inoperative.
Moreover, many of these previously known bypass valves simply comprise a valve member urged against a seat by a helical spring or other conventional resilient means. The valve member, which is of a relatively small area, forms the entire pressure sensing means and, due to its relatively small area size, the bypass valve member opens only slightly and somewhat spasmodically. Consequently, the fluid flow through the filter device, even with the bypass valve in its open position, is often at a lower than desired flow rate.
A still further disadvantage of these previously known bypass valves is that such bypass valves are typically secured directly to and within the housing for the fluid device. Consequently, when maintenance and/or cleaning of the bypass valve assembly is required, time consuming disassembly of virtually the entire fluid filtering device is usually required. Such disassembly of the fluid filter device also results in expensive and prolonged downtime for the hydraulic system.
A still further disadvantage of these previously known filtering devices, particularly when used as a suction line filter, is that entrained air is permitted to accumulate in pockets at high points and then pass in significant quantities. Cavitation is then experienced in pumps with eventual erosive damage. Noise occurring during such cavitation frequently results in considerable time loss and labor cost looking for nonexistent air leaks.